Natural Versus Anthropogenic Factors Affecting Low-Level Cloud Albedo over the North Atlantic

Science ◽  
1992 ◽  
Vol 256 (5061) ◽  
pp. 1311-1313 ◽  
Author(s):  
P. G. Falkowski ◽  
Y. Kim ◽  
Z. Kolber ◽  
C. Wilson ◽  
C. Wirick ◽  
...  
Keyword(s):  
North Atlantic ◽  
Anthropogenic Factors ◽  
Factors Affecting ◽  
Low Level ◽  
Cloud Albedo ◽  
The North ◽  
The North Atlantic

scholarly journals Modelling Hydrometeorological Extremes Associated to the Moisture Transport Driven by the Great Plains Low-Level Jet

2021 ◽  
Author(s):  
Luis Gimeno-Sotelo ◽  
Patricia de Zea Bermudez ◽  
Iago Algarra ◽  
Luis Gimeno
Keyword(s):  
Great Plains ◽  
North Atlantic ◽  
Source Region ◽  
Lower Troposphere ◽  
Dynamical Instability ◽  
Low Level ◽  
Extremal Dependence ◽  
The North ◽  
Low Level Jet ◽  
The North Atlantic

Abstract The Great Plains Low-Level Jet system consists of very strong winds in the lower troposphere that transport a huge amount of moisture from the Gulf of Mexico to the American Great Plains. This paper aims to study the extremes of the Transported Moisture (TM) from the GPLLJ source region to the jet domain; and, for low and high TM, to analyze the extremal dependence between the upper tail of the precipitation in the GPLLJ sink region and the lower tail of the tropospheric stability in that region (omega). The declustered extremes of TM were analyzed using Peaks Over Threshold (POT). A non-stationary Exponential model was fitted to the cluster maxima. Estimated return levels show that the extremes of TM are expected to decrease in the future. This is meteorologically congruent with the known displacement of the western edge of the North Atlantic Subtropical High, which controls atmospheric circulation in the North Atlantic, and to a higher scale with the change of phase from negative to positive of the Atlantic Multidecadal Oscillation. Bilogistic and Logistic models were fitted to the extremes of (-omega, precipitation) for low and high TM, respectively. The extremal dependence between "-omega" and precipitation proves to be stronger in the case of high TM. This confirms that dynamical instability represented by “-omega” is the most important parameter for achieving high values of precipitation once there is a mechanism that allows the continuous supply of large amounts of moisture, such as the derived from a low-level jet system.

scholarly journals On the Seasonal and Synoptic Time-Scale Variability of the North Atlantic Trade Wind Region and Its Low-Level Clouds

2015 ◽  
Vol 72 (4) ◽  
pp. 1428-1446 ◽  
Author(s):  
Matthias Brueck ◽  
Louise Nuijens ◽  
Bjorn Stevens
Keyword(s):  
Wind Speed ◽  
Time Scales ◽  
North Atlantic ◽  
Large Scale ◽  
Sensible Heat Flux ◽  
Cloud Amount ◽  
Trade Wind ◽  
Low Level ◽  
The North ◽  
The North Atlantic

Abstract The seasonality in large-scale meteorology and low-level cloud amount (CClow) is explored for a 5° × 5° area in the North Atlantic trades, using 12 years of ERA-Interim and MODIS data, supported by 2 years of Barbados Cloud Observatory (BCO) measurements. From boreal winter to summer, large-scale subsiding motion changes to rising motion, along with an increase in sea surface temperature, a clockwise turning and weakening of low-level winds, and reduced cold-air advection, lower-tropospheric stability (LTS), and surface fluxes. However, CClow is relatively invariant around 30%, except for a minimum of 20% in fall. This minimum is only pronounced when MODIS scenes with large high-level cloud amount are excluded, and a winter maximum in CClow is more pronounced at the BCO. On monthly time scales, wind speed has the best correlation with CClow. Existing large-eddy simulations suggest that the wind speed–CClow correlation may be explained by a direct deepening response of the trade wind layer to stronger winds. Large correlations of wind direction and advection with CClow also suggest that large-scale flow patterns matter. Smaller correlations with CClow are observed for LTS and surface evaporation, as well as negligible correlations for relative humidity (RH) and vertical velocity. However, these correlations considerably increase when only summer is considered. On synoptic time scales, all correlations drop substantially, whereby wind speed, RH, and surface sensible heat flux remain the leading parameters. The lack of a single strong predictor emphasizes that the combined effect of parameters is necessary to explain variations in CClow in the trades.

scholarly journals Annually resolved Atlantic sea surface temperature variability over the past 2,900 y

2020 ◽  
Vol 117 (44) ◽  
pp. 27171-27178
Author(s):  
Francois Lapointe ◽  
Raymond S. Bradley ◽  
Pierre Francus ◽  
Nicholas L. Balascio ◽  
Mark B. Abbott ◽  
...  
Keyword(s):  
North Atlantic ◽  
High Arctic ◽  
Sea Surface ◽  
Anthropogenic Factors ◽  
Multidecadal Variability ◽  
The Past ◽  
The North ◽  
The North Atlantic ◽  
Atmospheric Circulation Anomalies ◽  
Natural Climate

Global warming due to anthropogenic factors can be amplified or dampened by natural climate oscillations, especially those involving sea surface temperatures (SSTs) in the North Atlantic which vary on a multidecadal scale (Atlantic multidecadal variability, AMV). Because the instrumental record of AMV is short, long-term behavior of AMV is unknown, but climatic teleconnections to regions beyond the North Atlantic offer the prospect of reconstructing AMV from high-resolution records elsewhere. Annually resolved titanium from an annually laminated sedimentary record from Ellesmere Island, Canada, shows that the record is strongly influenced by AMV via atmospheric circulation anomalies. Significant correlations between this High-Arctic proxy and other highly resolved Atlantic SST proxies demonstrate that it shares the multidecadal variability seen in the Atlantic. Our record provides a reconstruction of AMV for the past ∼3 millennia at an unprecedented time resolution, indicating North Atlantic SSTs were coldest from ∼1400–1800 CE, while current SSTs are the warmest in the past ∼2,900 y.

scholarly journals Linearity of the Atmospheric Response to North Atlantic SST and Sea Ice Anomalies

2005 ◽  
Vol 18 (12) ◽  
pp. 1986-2003 ◽  
Author(s):  
Sébastien Conil ◽  
Laurent Z-X. Li
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Geopotential Height ◽  
Winter Season ◽  
Low Frequency ◽  
Temperature Response ◽  
Low Level ◽  
The North ◽  
The North Atlantic

Abstract The observations of the ocean–atmosphere–sea ice have recently revealed that the oceanic surfaces can have a subtle but significant impact on the atmospheric long-term fluctuations. Low-frequency variations and long-term trends of the North Atlantic atmospheric circulation have been partly related to particular SST and sea ice features. In this work, the influence of typical tripolar SST and dipolar sea ice anomalies in the North Atlantic–Arctic on the atmosphere is investigated. A large ensemble of AGCM simulations forced by three different anomalous boundary conditions (SST, sea ice, and SST + sea ice) are used. The linearity of the simulated response in the winter season is particularly assessed. In these experiments, while the winter low-level temperature response is mainly symmetric about the sign of the forcing, the asymmetric part of the geopotential response is substantial. The sea ice forcing maintains a baroclinic response with a strong temperature anomaly in the vicinity of the forcing but with a weak vertical penetration. The SST maintains an NAO-like equivalent barotropic temperature and geopotential height response that extends throughout the troposphere. It is also shown that the combination of the two forcings is mainly linear for the low-level temperature and nonlinear for the geopotential height. While the SST forcing seems to be the main contributor to the total temperature and geopotential height responses, the sea ice forcing appears to introduce significant nonlinear perturbations.

scholarly journals Oceanic changes in the Sargasso Sea and declines in recruitment of the European eel

2007 ◽  
Vol 64 (3) ◽  
pp. 519-530 ◽  
Author(s):  
Kevin D. Friedland ◽  
Michael J. Miller ◽  
Brian Knights
Keyword(s):  
North Atlantic ◽  
Mixed Layer Depth ◽  
Life Stage ◽  
Larval Survival ◽  
Larval Transport ◽  
Anthropogenic Factors ◽  
European Eel ◽  
Sargasso Sea ◽  
The North ◽  
The North Atlantic

Abstract Friedland, K. D., Miller, M. J., and Knights, B. 2007. Oceanic changes in the Sargasso Sea and declines in recruitment of the European eel. – ICES Journal of Marine Science, 64: 519–530. Anguillid eel recruitment in the North Atlantic has declined in recent decades, raising concerns that climatic changes in the Sargasso Sea may be influencing oceanic reproduction and larval survival. There is a significant negative correlation between the North Atlantic Oscillation and long-term variations in catches of glass eel stages of the European eel Anguilla anguilla recorded by the fishery independent Den Oever recruitment index (DOI) in the Netherlands, lagged by one year. Ocean-atmospheric changes in the Sargasso Sea may affect the location of spawning areas by silver eels and the survival of leptocephali during the key period when they are transported towards the Gulf Stream. A northward shift in a key isotherm (22.5°C), defining the northern boundary of the spawning area, a declining trend in winds and transport conditions in larval transport areas, and a shallowing of the mixed layer depth could affect primary productivity in areas where leptocephali feed. The relationships between these ocean parameters and the DOI suggest that these changing ocean conditions could be contributing to declining recruitment of the European eel and probably also of the American eel (A. rostrata), but anthropogenic factors during their continental life stage must also be considered.

The distribution and variability of low-level cloud in the North Atlantic trades

2014 ◽  
Vol 140 (684) ◽  
pp. 2364-2374 ◽  
Author(s):  
L. Nuijens ◽  
I. Serikov ◽  
L. Hirsch ◽  
K. Lonitz ◽  
B. Stevens
Keyword(s):  
North Atlantic ◽  
Low Level ◽  
The North ◽  
The North Atlantic
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